Microstructural evolution and mechanical properties of CuW/CuCr interface with mixed powder interlayers by liquid diffusion bonding technique

Cu-W composites and CuCr alloy were bonded with mixed Cu-Fe powder interlayers using the liquid diffusion bonding technique at 1380 °C for 1 h. Microstructures of the CuW/CuCr joints with Cu-Fe powder interlayers were investigated and compared via field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. Tensile tests were examined to evaluate the resulting joints. The results show that a diffusion solution layer about 2-3 μm width formed at the Cu/W interphase and the interfacial strength can reach up to 400 MPa when Cu-3wt%Fe interlayer is introduced into the interfacial region between Cu-W and CuCr alloy. Furthermore, the interfacial fracture morphology presents more transgranular cleavage fractures of W particles. However, when the content of Fe in the powder interlayers is above 3 wt%, the interfacial strength decreases gradually with the increasing of Fe content. After Cu-15 wt%Fe interlayer was applied, Fe7W6 phase is found in W skeletons and micro-cracks appear at the CuW/CuCr interface. Therefore, the interfacial strength declines to 263 MPa. The fraction of cleavage fracture decreases and the cracks propagate cross different areas of the CuW/CuCr interface.